I am looking at the HS-422 and HS-485 servo motors from hitech.
My application requires the robot to make a small motion every 3 seconds. The motion itself can be completed in 1 second. This robot would need to run continuously 24x7 for 3 weeks.
Can the HS-422 and HS-485 stand up to such a demand. If not, are there other servos better suited for the task?
Unfortunately, there are not good answers about that.
A servo will fail mostly because it will be overheating and degrade. This can happen quick or over long time depending on the Load it will be carrying and the surrounding temperature.
This makes it really difficult to know if it will fail or not in your particular conditions.
One thing peoples do is to use an overkill servo for the application they are making which means it will not have to work as hard. (HS-645 maybe)